Rolling mill drive system

ABSTRACT

A ROLLING MILL STAND HAVING A PAIR OF SMALL DIAMETERWORK ROLLS EACH BEARING AGAINST BACK-UP ROLLS, EACH WORK ROLL BEING COUPLED TO A DRIVE MECHANISM THEREFOR, THE DRIVE MECHANISMS BEING SYNCHRONISED AND BEING ON OPPOSITE SIDES OF THE STAND.

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ROLLING MILL DRIVE SYSTEM lfled June 3,` 1969 3 Sheets-Sheet s United States Patent 3,605,474 RGLLING MILL DRIVE SYSTEM Bernard Lhenry, Le Creusot, France, assiguor to Creusot-Loire, Paris, France Filed June 3, 1969, Ser. No. 830,022 Claims priority, application France, Nov. 15, 1968, 173,991 Int. Cl. B21b 35/00 U.S. Cl. 72-249 3 Claims ABSTRACT OF THE DISCLOSURE A rolling mill stand having a pair of small diameter work rolls each bearing against back-up rolls, each work roll being coupled to a drive mechanism therefor, the drive mechanisms being synchronised and being on opposite sides of the stand.

The invention relates to an improvement to a rolling mill drive system, of use more particularly in sheet rolling mills for cold-working high-precision thin and medium plates or sheets.

One known kind of such a mill comprises a pair of very small-diameter vworking rolls borne along their whole length by intermediate larger diameter rolls parallel to the working rolls and borne by parallel lines of large diameter idle rolls, which are disposed with very short intervals between them and borne in each interval by a bearing rigidly secured to the roll housing. In known variant constructions, each working roll can be associated with one or two sets of intermediate rolls; another possibility is for the working rolls to bear directly on the idle rolls borne by the stand.

The narrowness of the working rolls in such mills enables very hard products to be rolled, with a considerable thickness reduction at each pass. The rolling forces are not absorbed by the working rolls but are transferred to the intermediate rolls and stand via the back-up or idle rolls, with the result that despite their narrowness, the working rolls do not bend to any appreciable extent and the end product is of very regular flatness.

For improved stiffness, the dilerent rolls can be mounted in a solid unitary housing whose windows are limited to the passage of the sheet.

`Conventionally, mills of this kind for thin and medium plates are driven by a motor whose axis is parallel to the working-roll axis and which energizes a geared reducer having two branches each connected to one working roll by a universally jointed roll spindle or other kind of transmission permitting a slight angular displacement. In a sheet mill, all the power is applied to the working rolls, and the forces to be transmitted are so great that the gearwheels of the reducer branches need to have a relatively large diameter, with the result that their betweencentres spacing is much greater than the mean betweencentres spacing of the working rolls.

As a result, the roll spindles need to be relatively long so that they can work at small operating angles. Furthermore, the short distance between roll centres precludes the use of large diameter coupling boxes between the roll spindle and the corresponding working roll. In such cases the roll spindles and coupling boxes often experience twisting, more particularly as the result of alternate impacts due to repeated engagement of sheets being rolled with reversal.

During rolling the working rolls are in driving engagement with one another via the sheet, which they grip, and via the reducer gearwheels. The resilience of long roll spindles and narrow coupling boxes may produce ice variations in the distribution of drive torque to each working roll and may elongate the top and bottom of the sheet by diiferent amounts, thus causing the resilient system to vibrate, particularly since the reducer gears form a source of vibrations which can amplify this periodic movement. Vibrations of this kind result in irregularities in the surface texture of the rolled sheet.

These disadvantages increase with the working width of the mill and with the torque to be transmitted to the rolls. Rolling mills of this kind having a large working width have therefore had to be tted with working rolls of larger diameter than for narrow mills, thus losing much of the advantage of using narrow rolls.

The present invention obviates these disadvantages by enabling elements likely to bend to be strengthened and eliminating the danger'of unsatisfactory transmission of the drive torque to the working rolls. According to the invention the two working rolls are driven by two separate, identical and synchronised drives disposed one on each side of the rolling mill, the two rolls -being connected to their respective drives at opposite ends.

The invention will now be described in greater detail with reference to an exemplary embodiment shown in the drawings, lwhich relate to a cluster rolling milli.e., a mill in which each working roll is borne by only two lines of back-up rolls.

In the drawings:

FIG. 1 is a side view of the roll housing and some of the run-in and run-out tables;

FIG. 2 is a plan View of the same unit, and

FIG. 3 is a half-section through the roll housing and a half-end view of the housing along line III-III of FIG. 2.

For the sake of clarity, the back-up rolls are not shown in FIGS. 2 and 3.

With reference to the three figures simultaneously, the rolling mill comprises a unitary housing 1 in which two small-diameter working rolls 2 and 3 are disposed and bear on large-diameter back-up rolls 4, 5 and 6, 7 respectively.

Each working roll 2, 3 has at opposite ends a journal 8, 9 comprising a tenon or wobbler 10` releasably secured to the journal by conventional means. A socket 11 having internal teeth 12 is secured to tenon 10.

On each side of housing 1 a gate plate 13 is articulated round a horizontal shaft 14 engaging in two supports 15 rigidly secured to housing 1. A reducer comprising a worm vwheel 18 and worm 19v in a casing 20 is secured to plate 13, 'which is formed with 1a central orifice 16. Wheel 18 has a hollow internally splined hub engaged by an insert 21 bearing a sleeve 22 having internal teeth 23. Wheel 18 is connected to roll 2 by roll spindle 24. The same has a set of spherical teeth at each end, the sets engaging in the internal teeth 12, 23 of the members 11, 22 respectively. Spindle 24 is retained transversely by swivel joint 25.

On each side of the rolling mill, each drive shaft 2'6, which is rigidly secured to the -worm 19 of each reducer 20, is connected to an electric driving motor 30 by a universal telescopic transmission 31.

At the mill entry and exit the products rest on and are driven by roll tables 40. Rolls 41 thereof are driven stepwise through a reducer 42 by bevel gear sets 43 which are connected to one another and to reducer 42 by universal transmissions 44. Reducers 42 are driven by output shaft 45 of the nearest electric motor 30A via pulleys 46, 47 and toothed belt 48.

The gates 13 can be rotated around their shafts 14 by a reciprocating hydraulic actuator 50l connected to gate 13 at 51 and to housing 1 at 52. In the. operating position, each gate 13 is pressed `against the side of housing 1 by bolt 53.

The main advantage of the embodiment described is that the two working rolls are driven at opposite ends to one another. The elements 10, 11, 12 can therefore be generously dimensioned, to reduce twisting in the drive torque transmission without restrictions due to the corresponding elements of the other roll. Similarly, the reducer 20 can be disposed exactly on the axis of the mean position of the working roll which it is driving without thereby limiting the diameter of -wheel 18. The spindle 24 therefore operates at a very reduced angular misalignment-i-e., under optimum efficiency and strength conditions.

Another advantage arises from the two working rolls being driven by separate drives which are not mechanically interconnected. The two motors are electrically interconnected to ensure balanced speed and torque but with some provision for slip, and in operation fine synchronisation of the drives is provided purely by the rolled stock, no other mechanical connecting means being used.

The worm reducer enables each driving motor to be disposed longitudinally along the run-in or run-out table, resulting in considerable space-saving and more particularly a reduction in width, thus facilitating mill layout. This feature also enables the rolls of the run-in and run-out tables to be driven directly by one of the two main-driving motors, `with the result that a simple mechanical connection synchronises the tables with the working rolls to an extent suicient to cover all the thickness reductions of which the mill is capable.

Mounting the reducers on pivoting gates greatly increases `roll accessibility for maintenance and replacement. The roll spindle 24, between any reducer and the corresponding working roll can readily be disconnected while remaining rigidly secured to the reducer. Gate 13 and reducer gear 20 are then tilted, as shown at 55 in FIG. 3, into a special pit 56 covered by a removable oor 57. The universal joint 31 does not have to be dismounted for the purpose and remains available to take up misalignment between shafts 45 and 26 in all positions of the reducer.

The scope of the invention is not of course limited to the details which have been described and will not be departed from by embodiments which are only slightly different. For example, the mechanical connection between a reducer gear and the corresponding working roll can be of the universal type, and the gates supporting the reducer can be actuated by fully mechanical or pneumatic devices instead of the hydraulic actuators described. Similarly, the toothed belts driving the roll tables can be replaced by chains or suitable gear trains.

I claim:

1. A drive system for a sheet rolling mill for cold working thin and medium plates and sheets comprising a unitary housing, two small diameter working rolls in said housing, at least two lines of larger diameter rolls in said housing supporting said working rolls, two separate motor means mounted on said housing, one of said motor means being connected to one end of one of said working rolls and the other of said motor means being connected to the other end of the other of said working rolls, each of said motor means including an electric motor, a direction changing speed reducer for said electric motor, a coupling box mounted on said housing between said reducer and the adjacent end of said work roll, means for displacing said coupling box angularly, said electric motors being identical, an input axis for each of said reducers parallel to the direction of movement of the sheet through the mill, sheet run-in and run-out tables adjacent said housing and said working rolls, the motor shafts for said electric motors being parallel to said tables, an angularly displaceable transmission connected between each of said electric motors and the adjacent one of said reducers, driving means for said run-in and said run-out tables and means for connecting said electric motors to said driving means.

2. A drive system according to claim 1 each direction-changing reducer being mounted on a pivoting axis articulated round an axis parallel to the rolling mill axis.

3. A drive system according to claim 1 wherein, for each position of the pivoting units supporting the direction-changing reducers, the misalignment between the reducer input shaft and the output shaft of the corresponding main driving motor is less than the tolerable misalignment for the transmission connecting the two latter shafts.

References Cited UNITED MILTON S. MEHR, Primary Examiner U.S. Cl. XR. 72-242 

